1. Field of the Invention
The present invention relates to an inflatable cuff which is adapted to be wound around a body portion of a living subject in measuring a blood pressure of the subject, and also relates to an automatic blood pressure measuring apparatus including an inflatable cuff.
2. Related Art Statement
There is known an inflatable cuff for use in measuring a blood pressure of a living subject. The cuff has an inflatable chamber which inflates upon supplying thereto of a pressurized air. The cuff is used by being wound around a body portion of the subject so that it is inflated to occlude arteries of the body portion. For obtaining an accurate blood pressure of the subject, it is required that the cuff be wound around the body portion with an appropriate and uniform pressing force over the entire circumferential length of the body portion (e.g., upper arm).
However, the subject's body portion around which the cuff is wound does not have a precisely cylindrical shape and, in fact, it has the shape of a truncated cone. For example, regarding an upper arm that is commonly used as the body portion around which the cuff is wound, it is empirically known that a circumferential length of the arm measured at a proximal edge (i.e., edge nearer to the shoulder) of the cuff wound around the arm is greater than another measured at a distal edge (i.e., edge nearer to the elbow) of the cuff. In addition, a thicker arm has a greater difference between the above-identified two circumferential lengths. For winding a cuff around a thick arm with an appropriate, uniform pressing force over the entire circumferential length of the arm, it is required that the cuff be so wound as to comply with the profile of the arm. An appropriate winding of a cuff around a precisely cylindrical body portion could be effected in such a way that one of the opposite edges of the cuff cylindrically wound around the body portion is positioned in one plane perpendicular to the center line of the cylindrical cuff. However, in the case where a cuff is wound around a body portion having a truncated-conical shape, an appropriate winding of the cuff needs the skill of a user such as a doctor or a nurse because the cuff has no means to which the user can refer. Thus, in this case, an accurate blood pressure measurement may not be obtained.